In the field of printing, the most common type printer has been the printer which impacts against record media that is caused to be moved past a printing line or line of printing. As is well-known, the impact printing operation depends upon the movement of impact members, such as print hammers or wires or the like, which are typically moved by means of an electromechanical drive system and which system enables precise control of the impact members.
In the field of dot matrix printers, it has been quite common to provide a print head which has included therein a plurality of print wire actuators or solenoids arranged or grouped in a manner to drive the respective print wires a very short, precise distance from a rest or non-printing position to an impact or printing position. The print wires are generally either secured to or engaged by the solenoid plunger or armature which is caused to be moved such precise distance when the solenoid coil is energized and wherein the plunger or armature normally operates against the action of a return spring.
It has also been quite common to provide an arrangement or grouping of such solenoids in a circular configuration to take advantage of reduced space available in the manner of locating the print wires in that specific area between the solenoids and the front tip of the print head adjacent the record media. In this respect, the actuating ends of the print wires are positioned in accordance with the circular arrangement and the operating or working ends of the print wires are closely spaced in vertically-aligned manner adjacent the record media. The availability of narrow or compact actuators permits a narrower or smaller print head to be used and thereby reduces the width of the printer because of the reduced clearance at the ends of the print line. The print head can also be made shorter because the narrow actuators can be placed in side-by-side manner closer to the record media for a given amount of wire curvature.
In the wire matrix printer which is utilized for receipt and for journal printing operations, the print head structure may be a multiple element type and may be horizontally disposed with the wire elements aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner across the receipt or journal paper and wherein the drive elements or transducers may be positioned in a circular configuration with the respective wires leading to the front tip of the print head. In the wire matrix printer which is utilized for business forms or like record media printing operation, the print head may be oriented in a manner wherein the nose of the print head is pointed downward for printing on the form, slip or like media while the carriage and print head are moved above and across the form or media in the horizontal direction. Another arrangement provides for the print head to be oriented in a manner wherein the nose of the print head faces rearward in a horizontal direction from the front of the printer for printing on a slip or like form.
In the dot matrix printer which includes a print head of the circular configuration and multiple element type, there is a requirement for moving the print head and the print head carriage to appropriate and precise positions along the line of printing for dot matrix printing of alpha numeric characters or of graphics type characters.
Representative documentation in the field of print head carriage drive systems includes U.S. Pat. No. 3,472,352, issued to N. Kondur on Oct. 14, 1969, which discloses an endless timing belt, a print element having a home position, and a control system that includes a switch which responds to the home position and also to a predetermined movement of print element travel.
U.S. Pat. No. 4,044,881, issued to H. D. Chai et al. on Aug. 30, 1977, discloses a stepper motor and sensor elements movable with a print head carrier that senses the presence of teeth of a toothed stator bar to generate timing signals for controlling operation of the printer and motion of the carrier.
U.S. Pat. No. 4,076,111, issued to P. I. Robinson et al. on Feb. 28, 1978, discloses an opaque flag on the print head carriage that interrupts light from a LED from reaching a phototransistor when at the left hand margin.
U.S. Pat. No. 4,179,223, issued to O. Kwan et al. on Dec. 18, 1979, discloses left, center and right sensors for detecting the margins and the center location of the print carriage and shutter means mounted on the carriage for selection of the amount of travel of the carriage.
U.S. Pat. No. 4,284,362, issued to T. Jackson et al. on Aug. 18, 1981, discloses printer control logic for providing signals indicative of print head movement and operation of the print head.
U.S. Pat. No. 4,338,035, issued to H. Kondo et al. on July 6, 1982, discloses a printer with a movable print head carriage along with a slitted plate and a carriage position detector on the carriage and astride the slitted plate.
U.S. Pat. No. 4,543,644, issued to Y. Kozima et al. on Sept. 24, 1985, discloses a control circuit having a microprocessor, a RAM, a shift register and a DMA controller.
U.S. Pat. No. 4,602,882, issued to H. Akazawa on July 29, 1986, discloses a control circuit that detects the change of level of a home position signal in synchronism with a print position signal. A detector detects slots in a disk signaling print position.
And, U.S. Pat. No. 4,643,596, issued to T. Shimada et al. on Feb. 17, 1987, discloses a printer wherein a home signal is generated each time the print head leaves its home position. The printer uses a single detector cooperating with a slotted disk.